Today, ventilator-induced pneumonia is one of the leading causes of hospital deaths due to infections. Such infections are frequently referred to as nosocomial infections.
Mycoplasma pneumoniae is resistant to many antibiotics such as penicillin, cephalosporins, and vancomycin. M. pneumoniae causes a pneumonia often called “walking pneumonia” or “primary atypical pneumonia.”
Other cases of pneumonia can be causes by a number of species of bacteria, including, but not limited to, Streptococcus species, Staphylococcus species, Pseudomonas species, Haemophilus species, and chlamydia. 
The disease of pneumonia can be divided into two forms: bronchial pneumonia and lobar pneumonia.
Multiple antibiotic resistant forms of Streptococcus pneumonia that emerged in the early 1970s in Papua New Guinea and South Africa were thought to be flukes, but multiple antibiotic resistance now covers the globe and has rapidly increased since 1985. Increases in penicillin resistance have been followed by resistance to cephalosporins and by multidrug resistance. The incidence of resistance to penicillin increased from <0.02% in 1987 to 3% in 1994 to 30% in some communities in the United States and 80% in regions of some other countries in 1998. Resistance to other antibiotics has emerged simultaneously: 26% resistant to trimethoprim/sulfa, 30% resistant to cefotaxime, 30% resistant to macrolides, and 25% resistant to multiple drugs. Resistant organisms remain fully virulent.
Current treatment for airway infections is still with antibiotics. However the overuse of antibiotics is leading to a proliferation of antibiotic resistant bacteria. It has been known for many years that bacteria have the ability to spread antibiotic resistance from one species to another through the action of plasmids known as resistance transfer factors (RTFs). Of particular significance is the generation of plasmids that carry multiple resistance genes. These mechanisms are described in A. A. Sayers and D. D. Whitt, “Bacterial Pathogenesis: A Molecular Approach” (ASM Press, Washington, D.C. 1994), pp. 107-109, incorporated herein by this reference.
The reason that antibiotics are frequently ineffective in this clinical situation is that recently it has been discovered that bacteria are living in a dormant state inside a slimy biofilm. One example of such a biofilm occurs in the ear. The seemingly innocuous fluid behind the ear is actually a microbe-laden biofilm containing bacteria that become activated and grow rapidly under the right circumstances. This biofilm is also in the outer ear canal.
This revised understanding had come about because, previously, scientists studied bacteria in their free-floating form. Bacteria prefer the slimy, communal life because it protects them from toxins in the environment. Biofilm formation takes place in a step by step manner. First, inorganic or organic molecules are absorbed to a surface. This creates a conditioning layer that increases the ability of bacteria to attach to a surface. Once a conditioning layer is formed, bacterial adhesion follows. Live or dead cells will attach to surfaces with similar propensity. Bacterial attachment is mediated by fimbriae, pili, and flagella, and by extracellular polysaccharides.
When first formed, the bond between the conditioning layer and the bacteria is not strong and can be easily removed. With time however, these bonds are strengthened, making removal difficult. Once embedded within a biofilm, bacterial cells have an opportunity to repair cellular damage and to metabolize nutrients within the biofilm. As the biofilm continues to grow, the extracellular polysaccharides provide more and more protection. A biofilm is mature within 24 hours. Biofilm development can occur within one hour. After an eight-hour period, more than 91% of the bacteria are strongly attached within the biofilm. Killing bacteria within a biofilm requires up to 1000 times more antibiotic than is required to kill free-floating bacteria. The film physically prevents the antibiotic from reaching the bacteria. In addition, most bacteria in the biofilm are dormant and antibiotics typically only kill bacteria that are actively dividing.
Similarly, biofilms occur in the respiratory tract. Airway passages are coated with a slimy reservoir of hibernating bacteria. These inactive bacteria do not cause symptoms of an active infection but eventually they slough off and become free-floating active bacteria and cause another infection. This is one of the significant factors behind the existence of recurrent infections in such patients. Data show that bacteria incorporated in biofilms are more resistant than single cells and this is believed to be caused by physical protection by the biofilm matrix or by altered physiology of bacterial cells in the biofilm.
Bacteria have a natural tendency to attach to surfaces and to initiate the formation of a biofilm. The biofilm matrix is a collection of microcolonies with water channels in between and an assortment of cells and extracellular polymers such as polysaccharides, glycoproteins, and proteins. The different types of bonds between the saccharides give rise to a large number of different classes of polysaccharides including levans, dextrans, cellulose, glycogen, and alginates. Bacteria have the capacity to attach to and to colonize the surface of most materials. Attachment often results in the production of extracellular polysaccharides and changes in cellular morphology and growth rates. Different genes are expressed in bacteria that are attached to surfaces as compared to planktonic bacteria. As a result, surface-attached bacteria display increased resistance to toxic chemicals and biocides. While biocides have proven effective in killing free-floating bacteria, they are not effective in destroying bacteria within a biofilm. It becomes imperative that the biofilm be destroyed before the biocides can become effective.
There are many methods known to remove biofilms. The methods that are used to remove biofilm include the use of hypochlorite, hydrogen peroxide, ozone, detergents, or acids, the application of heat, the use of mechanical activity, or the use of ultrasound. Combinations of these methods are also used.
Many of these methods, although effective, are not suitable for use on biofilms that form on the body or within the body, such as in the respiratory tract. These methods are too harsh and disruptive of tissue for use in this context. A safe method is required to remove biofilms that form on the body or within the body.
Enzymes have been used to dissolve biofilms before, but not in the context of biofilms that form on the body or within the body. In laundry detergents, enzymes are used to remove deposits that may, in fact, be biofilms. Contact lens solutions use enzymes to remove the biofilm that can grow on a contact lens. In the dental field, dextranase and mutanase are used to remove plaque, a biofilm, from teeth.
Accordingly, there is a need for an improved method for removing biofilms that form on the body or within the body, particularly in airway passages. The improved method should be effective and safe. The improved method should also be compatible with antibiotics and other treatments for bacterial infection.